The present invention concerns the transfer of data from a first network which transfers data arranged in frames within which are not included source routing information, through a bridge, to a second network which requires frames to include source routing information.
For data transfer in some networks it is required that source route data be included with data frames. For instance, networks which are designed according to Draft Addendum to ANSI/IEEE Standard 802.5-1988 Token Ring MAC & PHY Specification Enhancement for Multiple-Ring Networks; Dec. 9, 1988, Prepared by the IEEE 802.5 Rapporteur on Multiple-Ring Networks; Institute of Electrical and Electronic Engineers, Inc., will be required to include source route data with each frame. This addendum to ANSI/IEEE Standard 802.5-1988 provides for a plurality of ring networks to be joined together by bridges. The source route data may contain a specific route through the network. Particularly, the source route data may contain a series of routing designators indicating which network rings and bridges the data frame is to travel through.
Alternately, the source route data may indicate that an explorer route is to be taken. Explorer routes are taken in order to discover a route from a source to a destination station. There are two types of explorer routes. The first type of explorer route is a spanning-tree route. Frames sent with a spanning tree route are relayed only by bridges designated as spanning tree bridges. These spanning tree bridges are chosen such that frames sent on a spanning tree route will appear once and only once on every network ring. Spanning tree routes are used by a source initiating a route discovery process.
The second type of explorer route is an all-paths route. A data frame with an all-paths route will be routed from along every non-repeating route in the network which is from the source of the data frame to the destination of the data frame. An all-paths route will be sent in response to route discovery frame on a spanning-tree route. The destination station of an all-paths route will receive as many frames as there are different routes from the source station to the destination station.